A DESCRIPTION OF THE YOUNG STAGES 

 OF THE WINTER FLOUNDER 



(Pseudopleuronectes americanus Walbaum) 



By W. E. Sullivan, 



Assistant Professor of Anatomy, Marquette University, 



School of Medicine, Milwaukee, Wis. 



The winter flounder (Pseudopleuronectes americanus 

 Walbaum) is of interest for two reasons: First it is typi- 

 cal of the group of flat-fishes or flounders in its meta- 

 morphosis; second, it is a fish of great commercial im- 

 portance. The flounders, as is well known, undergo a 

 peculiar metamorphosis. The young, so far as has been as- 

 certained, are symmetrical and swim upright; the adults 

 on the contrary show a lack of symmetry, most marked in 

 the position of the eyes and in the distribution of the 

 pigment, and swim on their sides. These facts at once 

 make the flounders of interest, and have made them ob- 

 jects of observation for half a century or more. Their 

 commercial importance has resulted in the perfection of 

 methods for their artificial rearing, and this insures a 

 ready and abundant supply of material. 



Revieiv of Literature. This has been abbreviated as 

 much as possible and incorporated in the text. There are 

 some papers, however, that require special mention. 



Agassiz's papers are the first works of importance on 

 P. americanus. There are two things that have led me 

 to believe that in the second paper Agassiz was not deal- 

 ing with the winter flounder. The size of the fish at 

 metamorphosis, as given by Agassiz, is much greater than 

 I found to be the case and there are many inexplicable 

 discrepancies in the plates. 



In the text we find "The young flounder has already at- 

 tained a considerable size before any signs appear of the 

 change of the position of the eye on the left side ; * * * 

 and before the young fish shows the least tendency to 



